1. Field of the Invention
Hydraulic positioning elements are completely filled with hydraulic fluid for locking the piston definitely in both axial directions when the passage through the piston is closed. On the other hand, the hydraulic fluid is subject to volume variations in response to varying temperatures. In order to prevent excessive pressure within the cylinder when the temperature rises and to prevent incomplete filling of the cylinder with hydraulic fluid when the temperature drops, temperature compensating means are provided.
2. Description of the Prior Art
From British Patent No. 676 254 a hydraulic positioning element is known, where for the compensation of the temperature-caused fluid expansion a compensation chamber is provided which comprises a partition which is axially movable and subject to the action of a return device. This compensation chamber is arranged in a hollow piston rod is in fluid-conducting communication with a working chamber. Thus this hydraulic positioning element is affected by relatively high construction expense.